declaring different type variables inside for condition in Java

Question

I know this is stupid, but it is sort of hard to research properly due to it's simple nature, I suppose.

for (char letter = 'a', int num = 1; maxLine - num > 0; letter++, num++) {
    System.out.print(letter);
}

This is a standard way to define variables inside a for condition for C and C#, but it doesn't seem to work here. Why?

can u ever define `int i =0 ,char c ='a';`?, don't think it works in c++ or c# — Ramanlfc, Mar 16 '16 at 15:11
Please don't add meta-tags like "" to titles. The correct way is to accept an answer, or - if the question hadn't been closed - posting your own answer (if none of the current answers suffice) and accepting it after the cooldown period. — Mark Rotteveel, Mar 17 '16 at 12:39
This question was wrongly closed. Its not a duplicate(or at least the duplicate cross is wrong coz that question refers to c++ not java). — theprogrammer, Jul 03 '20 at 03:31

score 1 · Answer 1 · edited May 23 '17 at 12:07

Because the variable declaration in a for loop follows that of local variable declaration.

Similar to how the following is not valid as a local declaration because it contains multiple types:

char letter = 'a', int num = 1;

It is also not valid in a for loop. You can, however, define multiple variables of the same type:

for (int n = 0, m = 5; n*m < 400; n++) {}

As to why the designers made it that way, ask them if you see them.

score 0 · Answer 2 · answered Mar 16 '16 at 15:10

This does not work in C/C++ either, not sure about C#, though.

The first part of your for statement might have multiple variables, but with the same type. The reason for this is that it is generally not possible to write:

int n = 0, char c = 5;

If you would like to do this, you needed two statements. Similarly, the first part of for only accepts one statement, so that you cannot put two ones in here.

declaring different type variables inside for condition in Java

2 Answers2